"Derivative of Hankel function of zeroth kind"
function diffhankelh1(n, z)
    if n != 0
        (hankelh1(-1 + n, z) - hankelh1(1 + n, z)) / 2
    else
        -hankelh1(one(n), z)
    end
end

"Derivative of Bessel function of first kind"
function diffbesselj(n, z)
    if n != 0
        (besselj(-1 + n, z) - besselj(1 + n, z)) / 2
    else
        -besselj(one(n), z)
    end
end
